The control of a flying aircraft is accomplished by aerodynamically effective control surfaces such as ailerons, flaps, tabs, rudder surfaces and elevator surfaces referred to herein as aircraft components or simply as control surfaces which are conventionally integrated into other aircraft components, e.g. wings and/or tail assemblies of an aircraft. Rolling motions of an aircraft are controlled by an aileron installed in each wing. Each aileron is normally connected to the respective wing trailing edge by a hinge that permits operating the aileron up or down for the intended influence on the flight situation.
Common to all control surfaces is the fact that these control surfaces have a relatively short length compared to the wing span of an aircraft while simultaneously having a large depth compared to the wing depth measured between the leading and trailing edge of the wing. As shown in FIG. 5 a control surface is normally connected to the wing by two hinges which provide a statically determined mounting. Due to the relatively small length of the control surface, such as an aileron, the difference between the deformation of the control surface, and the deformation or bending line of the wing also remains small. In such a mounting the bending of the wing in the z-direction is not imposed on the aileron, whereby no compulsion or unavoidable forces are generated in the aileron. Such forces would, however, occur for example in a mounting of the aileron to the landing flap with three hinges. Such unavoidable forces cause disadvantages which must be taken into account particularly where it is necessary to use slender control surfaces mounted with a continuous hinge connection formed by three or more hinges. In this connection the control surface under consideration has a length of about 4 m and a depth of about 0.4 m. Such a control surface technically also referred to as “tab” must be connected with more than two hinges to the wing or to the landing flap as shown in FIG. 6 in order to assure an aerodynamically satisfactory connection, whereby the hinge lines coincide as shown in FIG. 6 when the control surface is not deflected.
The aerodynamically exact mounting shown in FIG. 6 is achieved only by the use of at least three hinges, whereby it is unavoidable that compulsion forces are imposed on the control surface by the bending of the component to which the control surface is hinged. In addition to the compulsion forces generated by the bending of the wing or landing flap to which the control surface is hinged, compulsion forces are also generated by the bending of the control surface itself about its stiff axis which has a large moment of inertia when the deflection takes place while the hinge line is bent.
FIG. 7 illustrates the formation of compulsion forces in the aileron or tab due to the bending of the component to which the tab is secured by a continuous hinge. The wing or landing flap is bent upwardly, whereby compulsion forces generate pressure in the tab when the tab is deflected upwardly, causing a negative tab deflection. When the tab is deflected downwardly, in a positive tab deflection, tension forces would be generated in the tab. Thus, depending on the bending direction of the component to which the tab is hinged, and depending on the positive or negative tab deflection, pressure or tension forces will be generated in the tab. Such forces can damage the tab to the extent that it may fail unless countermeasures are taken. Such countermeasures call conventionally for either strengthening the stringers and/or ribs or installing additional stringers and/or ribs. In both instances additional weight cannot be avoided. Moreover, heavier tabs require higher actuator forces and larger mounting forces in the hinges must be taken up. Moreover, stiffer tabs may adversely influence the deformation characteristic and thus the aerodynamic characteristic of the component to which the tab is connected, for example a wing or a landing flap or tail unit.